Low water indicator



Sept. 5, 1933. E, w D 1,925,294

LOW WATER INDICATOR Filed May 16, 1932 Ei 7 Eduard L. \Jood Patented Sept. 5, 1933 1,925,294 Low WATER INDICATOR- Edward L. Wood, Detroit, Mich, assignor to Wood Hydraulic Hoist & Body Company, Detroit, Mich, a corporation of Michigan A Application May 16, 1932. Serial No. 611,650

l Claims.

Thisinvention relates to a low water indicator and safety appliance for boilers which is particularly useful in conjunction with boilers wherein oil, gas or the like is used as a fuel'and in which the supply of fuel maybe out off by suitable control devices, and which should be cut off in the event water in the boiler becomes low so as to expose the upper portion or crown of'the combustion chamber in the boiler to the intense heat of the burning fuel without a covering of water to absorb and take care of the heat. I

Under such circumstances, in a'relatively short time, the uncovered and exposed upper portions or crown of the combustion chamber will burn out with a resultant destructionof the boiler, at least until the combustion chamber is replaced,

The present invention is directed to a very simple and practical device for taking care of this condition and one which has proved especially useful and valuable in practical service. An understanding of the invention may be had from the following description, taken in connection with the'accompanying drawing, in which,

Fig. 1 is a fragmentary transverse section through a boiler equipped with the low water indicator and safety device of my invention, and

Fig. 2 is a fragmentary elevation, partly in section, of the part of the device which is carried within the boiler.

Like reference characters refer to like parts in the figures of the drawing.

The boiler may include an outer shell 1 and an inner shell 2, the water which is to be heated being located in the space between the shells as indicated. at 3. It is within the inner shell 2 that the fuel is burned, the inner side of the shell 2 being in direct contact with the burning fuel and the high temperature products of combustion produced thereby. One place where the present invention has been used is in connection with boilers of the character shown in the patent to Jerome No. 1,804,777, issued May 12th, 1931.

With my invention at the upper portion and outside of the outer shell 1 an electric switch control mechanism 4 is mounted. This switch control mechanism is of an old and well known character, bought openly on the market, and its specific structure need not be shown and described. It is enough to say that upon operation of the switch there may be anautomatic closure of an electric circuit, the wires of which lead through an outlet 5 to any desired mechanism to be operated throughelectric current, and that such switch is adapted to be thermostatically operated, the device including a depending thermostatic element 6 which, in the combination disclosed, extends downwardly through the upper side of the outer shell 1.

The lower end of the thermostatic member 6 enters a cup '7 of metal which is welded or otherwise permanently secured in the upper portion as shown 'in'Fig. 1.

When the water is at the proper level it fills the cup 7 passing underneath the lower edges of the shell Swhich either-has spaces between its lower edges and the shell 2 to permit the water to enter said sleeve or, if desirable, the lower end of the sleeve 8 may be provided with a plurality of notches 9 making passages-for water entrance. So long as water is thus supplied to the cup 7 the temperature aii'ecting the thermostatic member 6 will not be sufficient to cause it to operate the electric switch apparatus at l.

However, when the water gets below a predetermined level, that is, below the upper end of the cup 7 such water as is in the cup 7 will be rapidly evaporated and the thermostatic member 6 subjected to very high temperature, whereupon the thermostatically controlled switch is closed to actuate whatever safety mechanism may be connected with its electric circuit. In oil burners for boilers, the closing or" the circuit may cause The sleeve 8 is of particular utility in devices 7 of this character in that as it serves as a shield or dam preventing water coming into contact engagement with the thermostatic member 6 which, without the sleeve 8, and under the strong ebullition of the water within the boiler and its eruption upwardly splashes against the thermostatic member and enters the cup '7 thereby defeating the purpose of the thermostatically closed switch mechanism, and subjecting the upper exposed part of the combustion chamber shell to the intense heat of the burning fuel; whereuponit is shortly destroyed.

With the construction which I have devised any upward eruption or splashing of the water as it is boiling strikes against the sleeve 8 and is returned back to the body of the water, and there is an immediate action of high temperature on the thermostatic member 6 as soon as the water within the cup 7 has boiled away, causing the operation of the electric switch with the consequent bringing into play oithe safety mechanism following operation of said switch. It will be noted that the sleeve 8 extends a considerable distance above the low water level so that any waves due to surging cannot pass over the upper end of the sleeve and contact with the thermostatic element to prevent its operation. Temporary rises or surges of the water merely cause a small flow of water through the restricted open ings and such is of toominute a' quantity to prevent operation of the thermostatic signal control.

The electric switch apparatusat i may operate either to open or to close the switch, it may be manually or automatically reset afteronce oper ated. In fact the switchmay be of any preferred type working in accordance with its design to serve its purpose and the structure of the switch itself is not specifically in any way concerned with the present invention.

The invention is defined'in the appended claims and isto be considered comprehensive of all forms of structure coming within their scope.

I claim:

1. In a boiler, an inner combustion chamber shell, an outer enclosing shell with a space between the shells wherein water is adapted to be heated, a. cup member inserted in the upper side of said inner shell and permanently secured in place with its upper end substantially in the same plane with the upper surface or" said inner shell, and a sleevebearing. upon said inner shell and located around and extending above the upper end of said cup, and means located close to the juncture between said sleeve and shell for admitting only a small amount of water to the interior of said sleeve and cup.

2. A structure containing the elements in combination defined in claim 1, combined with a thermostatic element extending through said sleeve and into said cup, and a device located outside of and mounted on the outer shell adapted to be operated by the thermostatic element upon subjecting said element toqhigh temperature.

3. In a boiler, an inner combustion chamber shell, an outer enclosing shell spaced from the inner shell, the space being adapted to contain water to be heated, a relatively small water receiving receptacle located so as to be heated by the products of combustion, and a member surrounding the-upper end of said water receiving 'member resting upon said inner shell and extending upwardly therefrom, said water receiving receptacles being continuously full when the level of water is higher than the upper end of said member, and said member preventing entrance of water into said receptacle from ebullition, splashing or the like when the level of the water is lower than the upper end of said water receiving receptacle.

4. In a boiler, an inner combustion chamber shell, an outer enclosing shell. with a space be-- tween the shells wherein water is adapted to be heated, av thermostatic element extending through the outer shell and into the space between. the shells and having a heat affected por-:

tion located adjacent the inner shell, a protecting member surrounding said thermostatic element and joining said inner shell and extending. upward an appreciable distance above the low Water level, and a restricted passage between the interior and exterior of said protecting member 

